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Are these aftermarket doors?

76k5blazerr

76k5blazerr

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Evening CK5, quick question. I’m looking at a parts truck tomorrow and was hoping to use the doors on a 73 K10 im restoring. Parts truck is a 74 c20. Has anyone ever seen a dimple on the inside of the doors like these have? Look right below the door panel? Think these are aftermarket? I’ve never seen anything like it before. I am wanting original. Thanks fellas.

53c1c5dc7088e64c713317c148d304b8.jpeg9a97f5263ccf79bb1be0271a003b7540.jpeg
 
I’m not able to see the pics since I’m a non-member, but an easy way to tell an aftermarket door is to tap in the center of the door on outside where it’s convexed to see if it sounds tinny. Or if you press on it lightly you’ll feel it push in. An OEM door is heavier gauge and sounds more solid. Give your doors a little tap and you’ll know what an OEM door sounds like.

Also, if you take a weak magnet (like a fridge magnet) you can check for bondo, or better yet get a coating thickness gauge like I have.
 
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I have never seen that dimple before. I see no reason to think that is not original paint based on those pics, but they are far from enough detail to know for sure.
 
kennyw said:
I have never seen that dimple before. I see no reason to think that is not original paint based on those pics, but they are far from enough detail to know for sure.
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Yeah I have never seen this either and I have had at least 100 vehicles pass under my hands
 
I think I have these on my doors, I will look today they have GM stickers on it.
 
I don't have any info on why, what year(s), what model(s), etc. But I skimmed through some trucks on BaT and found the below one with the same indentions. The doors on this truck appear to be original, but who knows.

https://bringatrailer.com/listing/1973-chevrolet-c20-pickup-13/

Hope it's not against the rules to link that on the forum, but it's a completed auction just for the sake of the pictures in it.
 
These are not the correct doors for your truck. These doors are 77 and up. That oval shaped dimple that I circled is the dead giveaway. Someone has gone through the effort to make them fit a 73 to 75 door panel. See the pictures I attached below for reference. Most likely if those doors are on a 73 to 75 truck, they were used because the 73 to 75 doors were notorious for rusting out even worse than the later model version. I don't think I've seen a set that wasn't rusty on a truck here down south.

Screenshot_20251109-205235.png

Screenshot_20251109-205346.png
 
But in order to make them work for 73-75, they would have had to fill in all of the extra holes and that would not be easy. There would be evidence of welding and/or bondo in that case.

My guess would be GM replacements made for 1973-76 applications, produced from late 1976-80ish added that dimple due to the way the tooling was modified for 1977+ doors. Due to the high cost of the tool, they likely modified the old tool rather than made a new one from scratch. All of the extra holes for the 77+ door panels were probably stamped out of the inner panel on a different tool than the one that formed the first shape. I have no way to prove any of that, it is just coming from experience on how expensive tooling is for steel stamping and GM has other examples of this type of change like the 79-80 hood lips.
 
kennyw said:
But in order to make them work for 73-75, they would have had to fill in all of the extra holes and that would not be easy. There would be evidence of welding and/or bondo in that case.

My guess would be GM replacements made for 1973-76 applications, produced from late 1976-80ish added that dimple due to the way the tooling was modified for 1977+ doors. Due to the high cost of the tool, they likely modified the old tool rather than made a new one from scratch. All of the extra holes for the 77+ door panels were probably stamped out of the inner panel on a different tool than the one that formed the first shape. I have no way to prove any of that, it is just coming from experience on how expensive tooling is for steel stamping and GM has other examples of this type of change like the 79-80 hood lips.
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I wondered about some of this, but don't know enough about the tooling and stamping process. It sounds like something GM would do.

Do the original GM replacement doors have a GM stamp like the 73-80 fenders do?

Remember too, we're going off of one picture of a white door. In real life it may not look great or running your fingers across where those holes should be may reveal the truth.
 
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Were there any factory options to have a smaller door skin or even none at all? Some of the holes could have been a separate operation. It's also possible they were working on the door redesign before it happened and were set up to produce either. Tooling always wears out eventually and if it "was due", they may have jumped their newer/intermediate design.
kennyw said:
My guess would be GM replacements made for 1973-76 applications, produced from late 1976-80ish added that dimple due to the way the tooling was modified for 1977+ doors.
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What does the dimple do? Does part of the window mechanism mount there? Are there differences in which holes are present depending on power/manual?
 
At this point, it is all speculation. But I have never come across this dimple on doors that came with the truck from the factory for 73-76. I only speculate it showed up in a replacement senerio in the late 70s.

For 77+, I have never come across C/K 10-30 trucks with small door panels on original doors to the truck. In medium duty/heavy duty trucks there could be a possibility small door panels continued after 76 model year to use up some stock with doors like this as well. I know GM vans used 67-72 parts after the trucks changed to the new body style. We all know about K5/Suburban/Crew cabs carrying over squarebody designs when the light duty changed in 1988.

@sweetk30 has probably seen more medium duty GM trucks than anyone I know.
 
Blue85 said:
Tooling always wears out eventually and if it "was due", they may have jumped their newer/intermediate design.


What does the dimple do? Does part of the window mechanism mount there? Are there differences in which holes are present depending on power/manual?
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I looked through some of my photos and do not see the dimple or holes in the dimple being used for anything on 77+ doors. The reason I suspect they modified the 73-76 tooling for 77+ was the fact that they kept the profile of the 73-76 door panel along with all the mounting holes. I have seen many doors where people put the small panel on the newer door and it fit perfectly but left all of the extra holes exposed around the outside.

Eventually the tooling could have worn out and been replaced with new tooling. But it wasn't uncommon for that to happen after GM sold the tooling to an aftermarket company and stopped making parts for old models. Also, the process in which complex sheet metal is made, has several stations and several tools.

 
By the time i got in the square game here in the rust belt most 73-80 were junk and 81-up still decent . So i can not honestly say yes or no on 73-up to 80 ish . I can tell you unless someone add's around 1can or so of good rubberized undercoat to the outer door skin to add weight and make them swing and close like gm thats how i can spot them quick .
 
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